Diaphragm



July 18, 1933. M. NYSTROM DIAPHRAGM Filed April 10 192s 2 Sheets-Sheet 1 -35 r. A B

jfr

July 18, 1933.

M. NYSTROM DIAPHRAGM Filed April 10, 1926' 2 Sheets-Sheet 2 TOE/145K phragm mean; 18, 1933- 'IIYSTRGM, OF CHICAGO, ELLINOIS, ASSIGNQR,

UNITED RESEARCH CORPORATION, 0]? LONG ISLAND CKTY, NEW YGRK. A. COB-PORK TION 0F QELAWARE I mnrnnnerr Application fll'ec'l April 10,

My invention relates to devices for reproducing sound, and it has a special relation to sound boxes for'phonographs.

' be readily move-able to exert a piston-like objectionable 'tively thin metallic portion rigid with cenan stylus bar.

phragm. Fig.

awa

st lii action without itself flexing and setting up vibrations, and an outer relatral portion and readily flexible to facilitate the movement of the central portion.

A further object of the invention is to provide an interlocking joint for securing a central piston-like portion of a diaphragm to a flexible outer portion.

Other advantages ofthe invention will apar more fully as the description proceeds.

Referring to the accompanying drawings, Fig. 1 is an elevational view illustratin a sound box embodying the invention, detached from the tone arm. Figm2 is an elevational view of the opposite side of the sound box shown in Fig. 1. Fig. 3 is a sectional view of the soundbox takensubstantially on a line M of Fig. 1. Fig. 4 is a sectional view taken substantially on the line 4-4 of Fig. 1, and illustrating particularly a mounting for Fig. 5 is a detail central sectional view on a larger scale of the diaembodied in the sound box illus trated in Fig. 1. Fig.- 6 is a detail view on a-large scale of the outer side of the dia- 7 is a detail central sectional viewof a modified form of diaphragm, ind Fig. 8 is a detail view with parts bro en illustratingi a device for securing the bar tothe iaphragm. I Thesound box illustrated as embodying the invention cbmprises a casing, a diaphragm mounted in the casing, a stylus bar to faithfully rerare. Eerie]. Nb. 101,186.

1 to vibrate the diaphragm, and a mounting an inmate: nssrom we 2 (Fig. 2) for supporting the stylus bar for pivotal movement.

The diaphragm comprises a. central piston 3, and a flexible annulus 4, on which the piston 3 issupported in its vibratory movement.

To make the piston 3 of extremely low mass it is made extremely thin and is composed of a. light substance such as aluminum or an aluminum alloy. In order to prevent fiexure or the piston in operation and the setting up of undesirable vibrations therein it may be deformed. The central portion may be given the shape of a cone and a plurality of radial strengthening ribs 5 extending from the apex to the base of the cone may be provided to increase rigidity of the cone. Similarly shorter ribs 6 extending for a short distance from the base of the cone towar the apex may beprovided. In order tofur ther prevent fiexure of the piston 3, it may also have an annular deformation 7 therein which may be angularin cross section.

The piston 3 may be deformed at its periphery to provide for its securement to the annulus a, and the parts may be held together d'lu by an interlocked joint. A number of tongues 8 may be provided at this peripheral ortion a art he tongues 8 may extend radially along the,

opposite faces of the annulus 4.

The tongues may be formed by slitting the piston at its periphery by suitable dies and alternate tongues may be bent outwardly. The; annulus may be placed on the \mflexed tongues and the bent ton es may then be forced against the, face 0 the annulus and thus caused to securely grip the same.

The annulus 4 is extremely thin to facilitate flexiire thereof and is preferably made of alight material such as aluminum or aluminum alloy. To facilitate flexure of the annulus 4, ,a plurality of deformations may be provided which may annular concentric corrugations 10.

be in the shape of The corrugations 10 in the annulus may be formed by suitable diesl rior to the assemwise the'conical sha e of the piston, the ribs 5 and 6 and the de ormation 7 maybe produced by suitable dies rior to assembly.

The outer portion of the annulus 4 may be retained between a pair of washers 11 which may be compressed between a cap 12 and a plate 13. A clamping ring 14 having a threaded engagement with the cap 12 may be provided for holding the latter securely in osition.

11 aluminum diaphragm havin a central rigid portionapproximately .004 in thickness and an outer flexible portion approximately .002 in thickness has been foundto give excellent results.

Such a diaphragm embodying the invention, is extremely sensitive because of the exceedingly small mass of both the central and outer portions and the readily flexible characterof the exterior portion. It therefore, effects the faithful reproduction of. sound over a wide range of fre uencies without tendency to distortion or t e setting up of undesirable vibrations. 6

Yet, notwithstanding its extreme sensitive-- ness, it is very durable and shows no tendency to deteriorate even after long usage. The piston does not tend to collapse, but retains its shape rmanently.

In a mo ification of the invention, as shown in Fig. 7, a deformatibn 40 may be provided inan annulus 41 and a central piston 42 which may have the shape of a cone, may be secured thereto by tongues 43 adjacent the base of the cone. The tongues 43 may be similar to the ton ties 8 of the modification previously descr'%ed. Annulancorrugate deformations 44 may also be provided in the annulus 41 to facilitate flexure thereof.

The face of the plate 13 is spaced slightly from the diaphragm to provide a shallow air chamber and ma be provided with an annular recess 15 ad acent the outer 'base of thedeformation 7 to ermit the diaphragm to move toward the ate 13. The plate 13 me. also have an annu ar rib 16 adjacent the de ormation 7 which will permit. movement of the diaphragm but reduce the volume of the air chamber so that it may be made quite small. The inner face of the rib 16 may conver a into a throat 17 of small diameter.

or securing the stylus bard to the piston 3 the central conical portion of the piston may be provided with an aperture 18 adjacent its apex to receive the shank 20 of a rivet which may be provided witha head 21 for engaging the piston. The rivet may be composed of a light metal such as aluminum or an aluminum alloy and may clamp a ring 22 of suitable The stylus bar may be made of suitable material such as. steel andmay be ri idly securedto the ring 22 by solder 24. T stylus bar may be dished at 25 to provide room for the spread and of. the rivet and may have flattened terminals 26 seating snugly against ring 22.

It will be apparent that the described means for securlng the stylus bar to the diaphragm will have a minimum weight as the have a pair of oppositely exten ing tapere trunnions 27 thereon for supporting the same. Each trunnion may be surrounded by and rotate on a series of balls 28 in a bearing 30.0n the cap 12. A

follower 31 may be provided in each bearing,

having a recess 32 to receive the end of the trunnion 27. Each follower 31 may have a 1c)irl(iular tapered portion for engaging the A single leaf sprin may be provided for 7 strain and is permitted to move frictionlessly in its vibrations.

A feature of the stylus bar mounting is the tendency to automatically take up looseness of the balls ortrunnions. The spring urged followers maintain the balls constantly in intimate contact with the tapered trunnions so that the possibility of chattering and setting up undesirable vibrations in the movement of the stylus bar is eliminated. The spring pressure is light and the taper ,of the trunmons is such as to revent undesired wedging of the balls or t e development of friction which would interfere with the free movement of the stylus bar.

The bearings 30 may have longitudinal grooves 36 therein in which the spring may be seated, and the spring may be bowed centrally at 37 toimpart resiliency to it, and facilitate its assembly and secure retention in place.

phragm and 'within the scope of the appended claims.

' .002 in thickness I claim:

1. A- diaphragm comprising a single ply central portion approximately .004" in thickness, and an outer havin facilitate flexure, both 0 said portions being composed of a metallic substance as light in Weight as aluminum.

2. A diaphragm comprising a central rigid member, and an outer annular member, said central member having radially extending portions spaced apart to receive and grip said outer member therebetween and of sufiicient rigidity to securely hold said outer member by reason of the mechanical or gripping action or said'portions.

3. A diaphragm comprising a central rigid member having a deformation therein to prevent fiexure thereof, and an outer relatively thin flexible member having an opening therein to receive said central member, both of said members being metallic, said central member having radially extending tongues portion approximately. a deformation to thereon to grip opposite faces of said outer member, and secure said members together.

4. The method of making a diaphragm which comprises assembling an outer diaphragm member having an openin therein about a central diaphragm mem r, and bending one of said members to'cause' it to grip the adjacent edge of the other and secure said members together.

5. The method of making a diaphragm which consists in bending a peripheral portion of aoentral diaphragm member inwardly to permit the assembly of an outer annular diaphragm member against another peripheral portion of said central member, assembling said outer member in position against the second mentioned peripheral portion, and bending the first mentioned per1pheral portion to cause it to grip said outer member.

6. lhe method of making a diaphragm which comprises cutting radial slots in a rigid central diaphragm member to produce a series of radially extending tongues, flexing alternate tongues to permit the assembl of an outer diaphragm member against the unfiexed tongues, positioning said outer diaphragm member against said unflexed tongues, and flexing the bent tongues to cause them to grip said outer member.

MARTIN NYSTROM. 

